In retail establishments like grocery stores and department stores, receipts are given to customers when they have purchased goods as a way for the retail establishments to provide written acknowledgment that the customers have purchased the goods. The customers can then use the receipts to return the purchased goods if needed, to receive rebates on the goods, and to provide proof of when they purchased the goods should warranty repair be needed. The receipts are commonly printed as the customers are checking out of the establishments.
Indeed, in some countries, such as Italy, receipts are considered legal tax documents. If a customer cannot present a receipt showing that tax has been paid on a purchase, the customer can be fined by the government. The retail establishment itself may also be fined if it does not provide the customer with a receipt.
One typical way by which receipts can be printed relatively quickly and relatively silently is by using a thermal printing device. Unlike other types of printing devices that employ some type of colorant, such as ink or toner, to print onto media like paper, thermal printing devices do not use any type of colorant to print onto the media. Therefore, while printing devices like inkjet and laser printing devices have to have their colorant such as ink or toner periodically replenished, thermal printing devices do not.
Rather, a thermal printing device selectively heats media to print a desired image on the media as the media moves in relation to the printing device. The media darkens where it has been exposed to heat. The media used within thermal printing devices is thus a special type of media that is known as thermochromic media or more simply as thermal media, which is impregnated with a chemical that darkens when exposed to heat. While other types of printing devices may be able print on nearly any type of media, thermal printing devices thus have to use thermochromic media.